A vertical stabilizer in prior art usually consists of a centre box, a nose edge that is arranged on the centre box and aligned in the flow, and a rudder that is arranged on the opposing side of the centre box and pivoted around a hinge axis. Given a deflection of the rudder, the vertical stabilizer is exposed to air loads independently of the rudder angle, which lead to a torsion moment and bending moment. In order to roughly determine these moments on the centre box, a pressure point is assumed for the centre box, at which all air loads converge to exert a point force. Based on this assumption, it becomes clear that the magnitudes of the torsion and bending moments depend on an aerodynamically predetermined sweep angle of the vertical stabilizer, since as the sweep angle grows, so too does the distance between the pressure point and a midpoint on a centre box surface directed toward the aircraft fuselage. In transonic aircraft, the sweep angle is especially pronounced, and very high torsion and bending moments may arise in particular in larger commercial aircraft with very large rudder areas, which have to be completely absorbed by the centre box from a mechanical standpoint.
The centre box is dimensioned subject to several boundary conditions, which encompass not only aerodynamic, but also mechanical and geometric limitations, resulting from the arrangement of rudder actuators in the vertical stabilizer. In particular given large rudders with a prescribed hinge axis, actuators arranged perpendicular to the hinge axis, and the necessary actuator size, this may place tangible limitations on the space available for a centre box.
US 2010/0096497 A1 depicts several variations of drive kinematics for rudders, which reveal claddings for rudder actuators that are effective in terms of structural mechanics, and may mechanically shift as the rudder moves.
In addition, EP 763 465 B1 and U.S. Pat. No. 6,206,329 B1 show a typical arrangement of three actuators, which together move a rudder pivoted around a hinge axis.